CarbohydratesFunctionsMain source of energy for cellsSpare proteinAdd bulk to foodsProvide fiberSourcesGrains, fruits, dairy productsSimple carbohydrates: sugarsMolecule with 6 carbon atoms & oxygen and hydrogenComplex carbohydrates: starches & fiberSometimes called polysaccharidesLong chains of sugar unitsMonosaccharidesSix carbon moleculesGlucose- the body’s predominant fuelFructose- fruit sugarGalactose- one of the two components of the milk sugar lactoseDisaccharidesSucrose: a combination of glucose and fructoseLactose: a combination of glucose and galactoseMaltose: a combination of glucose and glucosePolysaccharidesGlycogenAnimal starch: configured in long chains of glucose moleculesThe body’s storage form of carbohydrateStarch from plant sourcesFiberPlant material: long chains of glucose molecules whose structure is resistant to enzymatic degradationCellulose, hemicellulose and pectinCommon dietary carbohydrate sourcesRice, wheat, maize, potato, apple, orange, grapes, cane, beet, honey, corn syrup, milkHow carbohydrate in food becomes glucose in the bodyFiber, starch, and sugars enter small intestinePancreatic amylase breaks down starch to disaccharidesEnzymes (disaccharidases) on intestine wall break down di- to mono-saccharidesMonosaccharides enter capillary – go to liverLiver converts galactose and fructose to glucoseFiber travels through unchanged to colonLactose intoleranceDeficiency in the enzyme lactaseSymptoms include nausea, diarrhea, and gasEffects ~80% of world populationCan be induced in remainder of population by substrate inductionUndigested lactose becomes fuel for intestinal bacteria that in turn produce gas and irritantsInfants and small children have the enzyme lactase so they can digest mothers’ milkDuring childhood, lactase begins to disappear in many peopleSome ethnic groups are more likely to develop lactose intolerance. By adolescence, it is gone in about 75% of African-Americans, Jews, Native Americans, Mexicans, and 90% of AsiansRegulation of blood glucoseAfter a meal, blood glucose risesPromotes an increase in insulin releaseInsulin promotes glycogen formationIn liver and muscleAfter a while, glucose levels fallPromoting glucagon releaseGlucagon stimulates glycogen conversion to glucose from liverGlucose metabolismGlucose enters the cell and is first divided into two 3-carbon fragments and energyThe 3-carbon fragments, called pyruvate, enter the mitochondria and are reduced to 2-carbon units called acetyl-coAThis process is done anaerobically and yields CO2 as well as 2 units of ATPThe acetyl-coA enter the Krebs Cycle and electron transport chain, which yields 32 ATP, CO2, and waterGlycogen Metabolism1/3 of all glycogen is stored in the liverthe other 2/3 is stored in muscleseach glycogen has many branches that stick outglucagon stimulates the breakdown of liver glycogen to glucose which can then enter the bloodstreamepinephrine stimulates the breakdown of muscle glycogen to glucose which can be used to produce ATP in the musclesNutrient Conversion to FatExcess carbohydrate intake is converted to fat in the liverAfter repleting glycogen storesAnd after restoring normal blood glucoseExcess protein and fat also can result in fat depositionThe liver releases these fatty acids into the bloodFat cells (adipocytes) take up these fatty acids and store themInadequate CHO in the dietWhen there is inadequate carbohydrates in the diet, the body has 2 problemsHaving no glucose, the body turns to protein and fat to make some glucoseWithout carbs in the diet, fat cannot be broken down completely for energy and the body converts its fats into ketone bodiesKetosis results when an undesirable high concentration of ketone bodies accumulate in the bloodMinimum amount sent by the DRI committee is 130 grams a day for an average-sized personDiabetesType 1- IDDMCharacterized by an immune response to pancreatic beta cellEventually the pancreas stops making insulinOften starts early in lifeType 2- NIDDMCharacterized by insulin resistance- the insulin is there, but it doesn’t work to foster glucose uptake by the cellsOccurs later in life (adult onset)Blood glucose valuesNormal: 100 mg/dLPrediabetes: 100-125 mg/dLDiabetes: 125 mg/dLComplication of diabetesBlindnessKidney diseaseHeart diseaseNerve damageIncreased infectionsAmputation of limbsAlternative sweetenersNaturally occurring sweeteners:Corn syrup (high fructose)MolassesLevulose (fructose or fruit sugar)HoneySugar alcoholsHigh fructose corn syrupUsed by body like any other sugarNo evidence that it is preferentially stored as fatConcern is the amount of added sugars in our diet, HFCS or “corn sugar” is just one of these added sugars (used by food industry b/c it is inexpensive)High fructose corn syrup and the environmentCorn is grown as monoculture which depletes soil of nutrients, requires higher amounts of pesticides and fertilizerProcessing corn into HFCS is energy intensiveScaling back on consumption of HFCS is good for you and good for the environmentFunctions of LipidsNatures way of condensing energy stores- also insulates/protects organsSource of calories (9 calories/gram)Flavor and tenderness of foodSlow stomach emptying, more satiatingSource of essential fatty acidsTypes of lipidsTriglyceridesPhospholipidsSterolsPhospholipidsGlycerol + 2 fatty acids + phosphorusPhosphorus part makes it soluble in waterFatty acids make it soluble in fatTherefore can serve as an emulsifierKey role is in cell membranesSterolsLarge molecules consisting of interconnected rings of carbon atoms with side chains of carbon, hydrogen, and oxygen attachedCholesterolFound in all animal cell membranesNonessentialForms plaques that cause atherosclerosisCholesterol serves as the raw material forBileVitamin DSteroid hormones including the sex hormonesTriglyceridesMain form of fat in foodMade up of glycerol backbone and three fatty acidsFatty acids classified by length (#) of carbon atoms, and location of double bonds, organization of hydrogen around the double bondsSaturated fatty acidA fatty acid carrying the maximum # of hydrogen atomsUnsaturated fatty acidA fatty acid with less than maximum hydrogen atomsMonounsaturated fatty acidPolyunsaturated fatty acidTrans fatty acidsFatty acids with unusual shapesArise when polyunsaturated oils are hydrogenatedAdvantage: control consistency and oxidation of fatsDisadvantage: increase LDLFound in margarines, shortenings, baked goodsEssential fatty acidsHumans lack synthetic enzymes
View Full Document
Unlocking...